1. Field of the Invention
This invention is in the field of Direct Reaction Fuel Cells used to convert chemical energy in high-hydrogen-content fuels directly into electrical energy without burning them for heat energy or reforming them for production of H2 and having means to provide relative motion between an electrode and an electrolyte—including means for rotating an electrode (U.S. Class 429/67-69, Int. Class H01M), to achieve accelerated chemical reaction rates promoted by Taylor Vortex Flows (TVF) and Circular Couette Flows (CCF).
2. Description of Related Art
Direct Reaction Fuel Cells (DRFC) such as Direct Alcohol Fuel Cells (DAFC), Direct Methanol Fuel Cells (DMFC), Direct Borohydride Fuel Cells (DBFC) that convert chemical energy in high-hydrogen-content fuels directly into electrical energy are well known. High-energy-content fuels include:                alkanes (paraffins)—methane, ethane, propane, butane, octane;        alcohols—methanol, ethanol, propanol, butanol;        kerosene; and        borohydrides—LiBH4, NaBH4, KBH4.These fuels are easily usable gasses, liquids or powders that can be dissolved in liquids. While they provide operational advantages over H2 fuel cells, existing DRFC have low energy and power densities per dollar that make them commercially uncompetitive.        
One reason that prior art DRFC cannot compete commercially with H2 fuel cells is that most existing DRFC require a solid polymer Proton Exchange Membrane (PEM) to prevent fuel-oxidizer crossover in electrolyte between anode and cathode electrodes. As a consequence, all commercially usable PEM for DRFC are based upon essentially acidic electrolyte because alkaline based membranes have not proven to be stable in DRFC environments. Extremely high temperature Solid Oxide Fuel Cells SOFC have limited application to DRFC and suffer from low power density due to the slow transport of ions across the solid membrane.
Acidic electrolytes in DRFC are slow and promote intermediate reaction products that increase polarization voltages at electrodes, which dramatically reduce power levels. Acidic electrolytes also support reactions that yield undesirable products that can poison electrodes and contaminate DRFC waste streams.
Hydrocarbon fuels, such as methane, alcohols and kerosene, and NaBH4 both have high energy densities per unit weight and unit volume. For example, methanol is capable of generating 1.21 volts and 6 electrons @ 700 kilo-Joules per mole (kJ/mole) and NaBH4 can provide 1.64 volts and 8 electrons @ 1271 kJ/mole based upon their respective reversible Gibbs free energies. Nevertheless, these yields cannot be obtained in prior art DRFC because hydrocarbons and NaBH4 have relatively slow oxidation catalyst reactions with acidic electrolytes that are required for use with PEMs.
Hydrocarbon and NaBH4 DRFC have potentials to produce markedly higher power and energy densities if an alkaline electrolyte could be used because polarization and poisoning would be reduced. However as described above, there are no durable alkaline-electrolyte-compatible ion exchange membranes that can prevent fuel-oxidizer crossover in higher power DRFC.
As described in Case A, fuel cells comprise an anode electrode reactive with a hydrogen-based or reducing fuel and a cathode electrode reactive with an oxidizer. The electrodes are separated from each other by an electrolyte fluid that transports, 1) protons from the anode to the cathode where they react with both the oxidizer and with electrons travelling from the anode through an external electrical circuit to the cathode to form a compound, such as water or 2) hydroxyl ions from the cathode to the anode to form water there.
Fuel cells rely on molecular kinetics, e.g., temperature, reactant concentration and catalysis to induce molecules to react at a catalytic surface. Prior art teaches that there are five principal methods to increase reaction rates and thereby increase output current. They are 1) raise temperature and/or pressure, 2) improve catalyst activity, 3) augment electrode surface activity by adding other forms of resonant energy to electrodes or to reactants (e.g., U.S. Pat. No. 7,482,072 to Brooks et al), 4) increase reactant transport rates to or from reaction surfaces (mass transport) and 5) raise the catalyst surface area/electrode area ratio.
Operational data for prior art fuel cell electric currents disclose that these currents do not exceed 1.0 ampere/cm2 and generally are in a range of 0.4 to 0.8 ampere under load at about 0.75 volt. This equates to about 0.3 to 0.5 watt/cm2 of anode or cathode surface. Some of the more common limits are imposed by a) mass-transport losses of ions moving through electrolytes, b) surface losses at catalysts caused by intermediate reaction products attracted to active sites, c) mass-transport losses of fuel, oxidizer and ions moving within electrodes to reach catalysts where they can react and d) overpotential decrement due to limited catalyst activity.